The drinking water in Graz stands out for its top quality. This is hardly surprising as a good third of it comes from the Hochschwab, that range of mountains in Eastern Styria from which Vienna is also supplied with outstanding water. The Hochschwab water which flows to Graz is directed to Graz by “Zentrale Wasserversorgung Hochschwab Süd Ges.m.b.H.” (ZWHS).
Large volumes of precipitation (up to 2000 mm every year) are the basis for the precious reserves of water in the Hochschwab. This liquid treasure – pure clear drinking water – is hidden deep below the rocks in the karst and in the aggregate. Dolines, ducts, crevices and cracks guide the rainwater and the meltwater into the interior of the mountain which is crisscrossed by a gigantic system of underground waterways and lakes.